This proposal for the Harvard Biomedical Informatics and Data Science Research Training (BIRT) program recognizes that the field of biomedical informatics is an increasingly relevant, if not essential, field for medicine and research in the health sciences. The practice of clinical care and biomedical investigation each constitute complex enterprises that are dependent on the mastery of enormous data streams. There is a crucial need for trained individuals who are able to integrate, interpret, and act upon the large-scale, high-throughput, and complex data that are generated in the course of biomedical research and the practice of medicine. The primary aim of this proposal is to contribute to the cadre of highly trained independent and successful researchers in the field of biomedical informatics. This proposal builds on the strengths of our many years of National Library of Medicine (NLM) fellowship training. The current proposed program will be overseen and administered by the Department of Biomedical Informatics at Harvard Medical School (HMS) and will involve collaboration with faculty at HMS and its affiliated hospitals, including Beth Israel Deaconess Medical Center, Boston Children's Hospital, Brigham and Women's Hospital, Dana Farber Cancer Institute, and Massachusetts General Hospital. In addition, the program will work closely with other Harvard University Schools in the university-wide data science initiative, and, in particular, with its Data Science Education Working Group, of which the proposed PI is a member. We meet all requirements of the current NLM RFA, which focuses on those informatics areas that directly pertain to health-related application domains. The breadth and depth of our research laboratories, real-world clinical systems, research activities, academic programs, and experienced faculty provide an outstanding environment to mentor and instruct trainees in all four of the NLM-identified focus areas ? healthcare informatics, translational bioinformatics, clinical research informatics, and public health informatics. We request support for a total of fifteen trainees per year: ten at the postdoctoral level and five at the predoctoral level. In addition, we propose to train four short-term trainees each summer. BIRT trainees work with internationally recognized faculty on high-profile grants and research projects. The program has a formal, required academic component, which includes the Master's degree for all postdoctoral trainees, and the PhD degree for all predoctoral students. Trainees' overall progression throughout the training period is closely monitored. Trainees are regularly evaluated through their course work and through progress on their research projects.